Failure mechanism for longitudinally stiffened I girders subjected to patch loading

Abstract

Investigation of the behaviour of plate girders (welded I girders) under the action of localized (patch) loading on a flange in the plane of the web is presented. Girders without vertical (transversal) stiffeners in the zone of load introduction, but with horizontal (longitudinal) stiffeners, are considered. An approximate solution for obtaining ultimate load is developed using failure (collapse) mechanism and following the upper bound theorem of plastic collapse. Procedure is based on the solution introduced by Roberts and Rocky and further elaborated by Roberts for the determination of the ultimate patch load for girders without longitudinal stiffeners. Procedure presented in this paper is adapted for the girders with longitudinal stiffeners. Proposed collapse mechanism is based on the experimental evidence. When the longitudinal stiffeners have enough rigidity, deformation at collapse, buckling of the web, is limited to the part of the web between loaded flange and longitudinal stiffener. Values of the ultimate loads obtained through developed procedure as well as the values from other, earlier authors’ proposal that was accepted and applied in the British standard BS 5400 are compared with the values from authors’ experiments and available database with the test results from other investigators.